This is a very good question and one I'm not sure I can explain. But I can give you my opinion, for what it is worth. I believe ghosts appear to certain people and not others for a few reasons: First the person they appear to is psychic. Secondly, the ghost may feel some sort of comradeship with the individual - meaning they can identify with the person for one reason or another. Perhaps because of age or because of something an individual is going through.

Additionally, some people can sense the presence of a ghost or spirit but not see them. While others can sense them as well as see them. This would likely depend upon the psychic capabilities of the individual.

There are so many variables that factor into the 'seeing' of ghosts and/or the hearing of ghosts that this question is difficult to answer. Though ghosts have been studied for many years; both from the layman's point as well as from the scientific point, we know very little about ghosts. No one can say for certain that ghosts are spirits or if they are electro-magnetic impressions from previous experiences in a specific location. As a result it is difficult to say anything for certain on the subject matter. Furthermore, the scientific world and the investigative world of the paranormal can't even begin to agree on whether ghosts are real or not. Because there is so much varying thoughts and opinions on the subject there are no set rules for anything regarding the subject. Clearly, I believe there are such things as ghosts. Having seen them since I was about six years of age I can't believe otherwise. But I could not prove to you or anyone else that they do exist - nor can I prove why the ghosts I've seen have made themselves visible to me and not to others. I can only assume the entities that have appeared to me do so because I am open to communication whereas others perhaps were closed off to communication at the time. Again, I can't stress enough that there is no set answer. But if your daughter is experiencing seeing ghosts then perhaps she should try to talk with the ghost that appears and find out what he/she wants and how she (your daughter) can help.

I hope this helps you. I'm not trying to be vague - I simply don't have a set answer for you.

An apparition, unlike a ghost, means the seeing of a spiritual being or ghost. Whereas a ghost can be heard, not seen, seen, not heard, or simply felt and not seen or heard. To see an apparition one must psychic. To feel a ghost is the lower form of an undeveloped psychic ability. Whereas seeing a ghost and hearing a ghost is a higher form of psychic ability. Psychic ability can be, many say, developed and there are many, many books written on the subject. 

In short trust your instincts - if your initial thought of a specific location is that it doesn't feel right then chances are it isn't right for you.